Yabo

Any idea where there is normally bad solder joints that people fix on these things/ Narrowed it down to DME.. Tap on it and the car no longer gets spark (still gets fuel)...

i can supply a picture of the dme if needed. I have it apart.

PorscheDoc

take good pics. They should be fairly obvious

Yabo

I'll get more of the rest of the board tonight, gotta go to work..

But i could get the car to die by wiggling around teh harness connector (had the board apart with the car running.. it seemed wiggling where the harness connects would make it die, seemed like it must be the pins from the connector into the board..

Heres the pictures of that area.. I don't see anything.. maybe you do?

V2Rocket

That is SO confusing....

If I were having DME problems I'd swap it out for one of the 4 spares I have

gregeast

CLICK HERE for a link to a write-up I did on my 951. Sharky did a nice write-up on an early DME, you might search for that if mine doesn't help.

2BWise

^^ He had a nice right up that pointed me where to look when I was having DME issues. If you're handy with a soldering iron you could go thru and resolder them all. It is time consuming but will make sure you get to all the possibilities.

triscadek

Is there a CB radio repair shop nearby? I've taken my cruise control box to a CB shop and got it resoldered for $10.

While you're at it clean the ground real good. A few years ago someone burned out a couple DMEs before he found out that a bad ground was at fault.

sharky47

http://www.rennspeedracing.com/DME_tutorial.html

Yabo

thanks.. v2, do you happen to have a spare i could buy that would work in an 85.5?

Yabo

sharky,... how much do you charge to do this?

Bri Bro

You have already done the hard part, you narrowed it down to the ignition circuit. The path you need to follow starts at pin 1 of the DME and goes to the T504 driver transistor. This is a large Transistor (package type TO3) that is mounted on a large heat sink. The marking for this part (T504) is printed beside the part on the printed circuit board. This is a common failure point, the solder connections develop small cracks due the thermal cycles, it is best to use a 10x magnifying lens to look for them.

Reflow the connection with new solder at least, it is better to remove the old solder first and then reflow with new solder. You can always take it to any electronic repair shop and have them reflow the bad solder connections. Once you have it apart, it sould take them a minute to repair the joints.

gregeast

^^^^ That's the one, it looks like this:

Yabo

pin 1 is the main ignition pin? thanks

Yabo

Fixed it, i think, i cant seem to get it to stall no matter how i smack, twist or dip in water (kidding) the dme while its running.

Upon closer look at those three solders that the main transistors legs go into , i could see circles in the solder (guessing they were cracks)... just to be sure had my dad touch them up with solder.. seems to have worked.. hopefully!

Thanks for the help.. another 200 dollar cost averted..

Yabo

was the three just like in this thread, so anyone searching this in the future...